DURING YEAR 2, WE WILL ATTEMPT TO DO THE FOLLOWING: 1. Construct new optical input to Quantimet and explore photographic and direct tissue viewing capabilities for counting and specify the receptor mosaic. 2. When techniques are sufficiently developed, do extensive quantification of receptor mosaic in 3-5 normal adult human eyes. 3. Describe the rod and cone mosaic in the adult rhesus. a. Check adequacy of procedures developed for human eyes when applied to rhesus, and correct any deficiencies. b. Do extensive quantification of receptor mosaic of 3-5 normal adult rhesus. 4. Develop techniques for doing SEM/Nomarski/LM/TEM observations on same piece of tissue. 5. Describe the rod and cone mosaic in the developing and geriatric human retina. a. Solve special problems encountered with very young and very old eyes. b. Do limited critical evaluation of mosaic at eight developmental ages (5 and 7 months of gestation, newborn, 6 month, 1, 3, 6, 12 years) using Nomarski, plastic embedded and SEM techniques. c. Do limited critical evaluation at four stages of aging (50, 60, 70, 80, years). 6. Describe the rod and cone mosaic in the developing and geriatric rhesus retina. a. Check adequacy of techniques worked out on humans to rhesus, and correct any deficiencies. b. Do limited critical evaluation of receptor mosaic at 4-5 developmental ages (birth, 2, 6, 12 months) and in fetus material if available. c. Do limited critical evaluation of receptor mosaic in aging rhesus at available ages (over 10 years of age). BIBLIOGRAPHIC REFERENCES: Adams, C.K., Perez, J.M. and Hawthorne, M.N. Rod and cone densities in the Rhesus. Investigative Ophthalmology, 11, 885, Nov. 1974.